This invention relates to the continuous winding of web materials, and particularly of thin plastic films such as stretch wrap and cling wrap films, as well as of paper, paperboard and other web type materials. In the continuous winding of such web materials, it is extremely important to maintain control over the tension in the web throughout as much as possible of the winding process, and particularly during the change from a full roll to a new core. This is particularly true with respect to the portion of the web which becomes the outer wraps on each full roll, and which, in the absence of proper tension control during roll changing, often becomes "tail waste" due to air entrainment between the outer web wraps that produces wrinkles, bunching, telescoping or skewing in this outermost portion of the roll.
Two co-owned patents disclose improvements of this aspect of continuous winding. The first of these patents Phelps et al U.S. Pat. No. 3,841,577, discloses a continuous winder wherein the full roll and the new core are each carried by a separate pair of turret arms that are mounted for rotation independently of each other and thus can be separately indexed to the various positions which they occupy during core loading, roll changing and the removal of a full roll.
The second such patent is Tetro U.S. Pat. No. 4,431,140, which discloses a turret-type winder wherein the winding roll and the new core are mounted at the opposite ends of a pair of rotationally mounted turret arms. Each of these turret arms also is provided with a rider roll which is carried by arms pivotally mounted on the turret arms for minimizing the amount of entrapped air between each winding wrap and thereby controlling the wound destiny of the roll. However, because the turret arms cannot be indexed with respect to each other, the angular distance through which they must rotate in the course of a roll change, as well as the distance between the new core and the full roll, are fixed and thus correspondingly affect web tension during roll changing.
A third co-owned patent, Tetro U.S. Pat. No. 4,422,586, discloses a continuous winder wherein severing the web at the time of roll changing is effected by a knife which is stationary at the instant when the web is being cut off, with the web being drawn across the knife edge immediately after it is affixed to the new core in order to cut the web at a location as close as possible to the new core. These provisions for severing the web do materially contribute to shortening the length of web upstream from the core, and thus the possibilities of folding back of the web at the start of the new roll, but otherwise the winder of this patent provides no control over the trailing portion of the web on the previous full roll other than is provided in Tetro U.S Pat. No. 4,431,140.
Thus while each of the above patents discloses a continuous winder which offers improvements over the art prior thereto from the standpoint of control of the tension in the web material during roll changing and correspondingly improving the properties of the successive wound rolls, there remains a need for a continuous winder which will still further reduce the length of the tail section of web that remains to be wound on the full roll after the web is cut, and which will also consistently reduce to a minimum the amount of web material between the cut leading end of the web and the area of web which is adhered to the new core at the start of a new roll.